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Full text of "An evaluation of nitrogen use in British Columbia agriculture ."

■ jf^ Agriculture 



Canada 

Research Direction generate ' • r ' 



Branch de la recherche 

Technical Bulletin 1987-3E 










An evaluation of nitrogen 
use in British Columbia 
agriculture 



AGRICULTURE CANADA 
CODE 8 7/0 3/12 NO. 



LIBRARY/BIELIOTHEOUE OTTAWA K1A OC5 




Canada 



The dots on the map represent Agriculture 
Canada research establishments. 



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An evaluation of nitrogen 
use in British Columbia 
agriculture 



C.G. KOWALENKO 

Research Station 
Agassiz, British Columbia 

Technical Bulletin 1987-3E 



Research Branch 
Agriculture Canada 
1987 



Copies of this publication are available from 

Dr.J.M.Molnar 

Director 

Research Station 

Research Branch, Agriculture Canada 

P.O. Box 1000 

Agassiz, B.C. 

VOM 1A0 

Produced by Research Program Service 

© Minister of Supply and Services Canada 1987 
Cat. No. A54-8/1 987-3 E 
ISBN 0-662-54839-6 



CONTENTS 



Summary, 4 

R6sum6, 5 

Acknowledgements, 6 

Introduction, 7 

Overview of agriculture in British Columbia in 
relation to nitrogen use, 7 

Review of nitrogen research conducted in British Columbia, 12 
Aridic - nonirrigated nitrogen management unit, 12 
Aridic - irrigated - extensive nitrogen management unit, 15 
Aridic - irrigated - intensive nitrogen management unit, 15 
Humidic nitrogen management unit, 18 

Outline of current system of recommendation, 23 

Assessment of fertilizer nitrogen use, 27 

Conclusions, 28 

References, 29 



SUMMARY 

A review of published research conducted in British Columbia 
showed that current nitrogen recommendations are largely supported 
by plant response data, with limited data on soils. As a result, 
the use of soil analysis for recommendations is theoretical. 
Comparisons of nitrogen fertilizer use with general recommendations 
showed that maximum rates of nitrogen are used in the Coastal and 
Okanagan areas, whereas significantly less than maximum recommended 
nitrogen fertilizer is used in the Interior and Peace River areas. 
When manure nitrogen is taken into account, rates of nitrogen well 
in excess of maximum recommendations are applied in the Lower 
Mainland and probably also in the Okanagan Valley. Research 
specifically aimed at the needs of each area of the province is 
reguired before extension work is conducted to either limit or 
increase nitrogen use. Soil nitrogen analysis should be included 
in future nitrogen research. Increased research should be 
conducted on biological fixation as a nitrogen source for crop 
production. 



r£sum£ 

line revue des recherches conduites en Colombie-Britannique revele que les 
recommandations actuelles de fumure azot6e sont bashes essentiellement sur la 
reaction des cultures, et beaucoup moins sur l'6tat du sol, de sorte que les 
analyses de sol n'ont qu'une utilite th^orique. La confrontation des 
pratiques de fumure avec les quantit^s recommand6es montre que c'est dans la 
zone cotiere et dans l'Okanagane que les doses maximales d' azote sont 
utilises alors que dans les regions de l'int6rieur et de la Riviere de la 
Paix on emploie des doses significativement inf6rieures aux doses 
conseill^es. Si l'on tient compte de 1' azote apport6 par le fumier, le 
Sud-ouest de l'int§rieur, et probablement aussi l'Okanagane, appliquent des 
doses d 1 azote bien au-dela des fumures maximales pr6conis6es. Des recherches 
sur les besoins particuliers dans chaque region de la province s'imposent 
avant qu'on puisse entreprendre de restreindre ou, au contraire, d'accroitre 
l'emploi de l'azote. Les recherches futures devraient tenir compte des 
r§sultats des analyses de sol. II faudra £galement intensifier les recherches 
sur la fixation biologique comme source d' azote pour les cultures. 



ACKNOWLEDGMENTS 

This report is the direct result of activities of the soil fertility work 
group of the soil management subcommittee. The subcommittee reports to the 
Land Research Science Lead Committee of British Columbia. The author wishes 
to thank all the members of the work group (Mr. R.A. Bertrand, Dr. A. A. Bomke, 
Mr. N.A. Gough, Dr. W.A. Herman, Dr. L.E. Lowe, Mr. S. Loewen, Dr. G.H. 
Neilsen, and Dr. W. van Lierop) and other soil scientists throughout the 
province for their encouragement and technical contributions in the 
preparation of this report. 



INTRODUCTION 

General aspects of the cycling of nitrogen in agriculture are fairly well 
understood (Stevenson 1982). Many processes are involved. Each process 
responds differently to environmental factors and farm management practices, 
and therefore the cycling of nitrogen is guite site-specific. As a result, 
extrapolation of nitrogen application practices and research information from 
one area to another must be done with extreme caution. Local evaluation is 
necessary to determine that the most effective methods are being used. 
Agriculture in British Columbia is diverse and in many ways unusual in Canada 
because of the topography and climate. Both economic and environmental 
pressures reguire increased efficiency in the use of nitrogen. Actual and 
recommended use should be examined and compared to achieve an accurate 
assessment of use in British Columbia. 

This report assesses current recommendations for nitrogen use by 
reviewing published reports of research conducted in British Columbia. 
Research journals are emphasized because they provide details of both methods 
used and interpretations, allowing the critical evaluation of data. A 
comparison is then made between actual and recommended use of nitrogen from 
available data. Although assumptions are reguired for the calculations, the 
data should provide an adeguate evaluation of the relative distribution of 
fertilizer nitrogen use. 

This evaluation of nitrogen use in British Columbia should provide a 
basis for improving current application practices through effective research 
and extension activities. It is hoped that the information is detailed enough 
to allow an exchange of knowledge and ideas within and beyond the borders of 
the province. 

OVERVIEW OE AGRICULTURE IN BRITISH COLUMBIA IN RELATION TO NITROGEN USE 

British Columbia has a diverse landscape and climate (Chilton 1981; 
Valentine et al . 1978), which has had a profound influence on the type and 
distribution of agriculture. The nitrogen cycle is dynamic and responds to 
climatic conditions. A general evaluation of nitrogen use in British Columbia 
would not be meaningful unless the diversity of agricultural activity is taken 
into consideration. 

Because of the cost of nitrogen fertilizer sources, loss of nitrogen from 
agricultural production systems is a major concern. Loss of nitrogen can 
occur through leaching, denitrification, volatilization, and erosion. In all 
of these processes, with the possible exception of volatilization, the 
moisture regime is the dominant factor influencing transformations and 
movement. Moisture is used as the dominant environmental factor for 
discriminating agricultural activity in relation to nitrogen use in this 
review. 

Census data from 1981 (Macey 1982), compiled for various census districts 
by regional district boundaries, were summarized into four larger areas: 
Coastal, Okanagan, Peace River, and Interior (Pig. 1). The Interior included 




Fig. 1. Outline of grouping of census-reporting districts into four general 
areas of agricultural activity and approximate distribution of land in 
agricultural reserves (shaded areas) in British Columbia. 



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Table 2. Distribution of farmland and irrigation in British Columbia in 1981 
and its average holding size and sales value.* 

(Lower Peace 

Coastal Mainland) Okanagan River Interior Total 



Total landf 


21 


934 


(2 


580) 


2 146 


19 


506 


45 


675 


89 310 


Land in farmsf 




164 




(101) 


162 




721 


1 


132 


2 179 


Improved farmland! 




115 




(81) 


72 




377 




382 


946 


Irrigation! 




13 




(8) 


28 




- 




60 


101 


Average holding size 




20 




(16) 


38 




385 




206 


109 


(ha) 























Total value of 488 (424) 114 60 138 799 

product sales 
(millions $) 

^Adapted frorrTMacey 1982. 
fin thousands of hectares. 



Table 3. Distribution of major crop production in British Columbia in 1981. 



(Lower Peace 

Coastal Mainland) Okanagan River Interior Total 



Cereal grains 


4 


596 


(3 440) 


5 


265 


144 


454 


15 488 


169 803 


Corn 


8 


008 


(7 466) 


1 


680 




6 


2 117 


11 811 


Alfalfa hay 


1 


752 


(1 097) 


16 


893 


28 


272 


69 009 


115 926 


Hay & other fodder 


42 


819 


(27 932) 


6 


576 


60 


431 


101 166 


210 992 


Vegetables 


6 


699 


(6 211) 




630 




15 


523 


7 867 


Tree fruits 




289 


(100) 


10 


437 




- 


791 


11 517 


Small fruits 


4 


260 


(4 137) 


1 


239 




2 


78 


5 579 


Total (ha) 


68 


423 


(50 383) 


42 


720 


233 


180 


189 172 


533 495 


Proportion of 




















improved farmland {%) 




60 


(62) 




59 




62 


49 


56 



Adapted from Macey 1982. 



10 



a plateau, a trench, and mountains. These areas reflect both the moderate, 
wet climate of the coast and the warm, drier climate farther east (Table 1). 
Because of its agricultural significance, the Lower Mainland was 
considered as a special area within the larger Coastal area. 

The statistics confirm that farms occupy only a small proportion of the 
total land mass of the province (Table 2). The Interior and Peace River areas 
tend to have extensive operations, with large holding sizes and a lower value 
of sales. The Coastal and Okanagan areas have smaller holding sizes and a 
high value of sales. This difference reflects the greater intensity of 
agricultural activity. The Lower Mainland tends to have the greatest 
intensity and generated over one-half of the total provincial sales of 
agricultural products in 1981. Irrigation is done not only in the Okanagan 
and Interior but also in the Coastal area. Despite the high precipitation on 
the coast, supplemental irrigation is used because of the low rainfall in July 
and August and the intensity of production. 

Cereal grains and grasses constitute the major crops grown in the 
extensive agriculture of the Peace River and Interior areas (Table 3). The 
Peace River is the major cereal-grain-producing area of the province. Grass, 
corn, vegetables, and small fruits are the major crops grown in the Coastal 
area, with many other crops produced because of the favorable climate. The 
Lower Mainland is the most important area for vegetable and small-fruit 
production. Production of tree fruits tends to be concentrated in the 
Okanagan Valley area, but many other crops are also grown there. Alfalfa 
accounts for a large proportion of the hay produced there. Over one-half of 
British Columbia's cattle were in the Interior in 1981, since this area is 
particularly suitable for extensive animal production (Table 4). However, the 
Coastal and Okanagan areas have a significant number of cattle, despite the 
smaller area of farmland. Much of the intensive cattle production consists 

Table 4. Distribution of the total number of cattle, hens, chickens, and pigs 
in British Columbia in 1981. 



Area 




Cattle 


Hens and 
chickens 


Pigs 




Coastal 
(Lower Main 
Okanagan 
Peace River 
Interior 


land) 


196 979 

(159 027) 

72 219 

81 649 

438 994 


8 997 163 

(7 991 733) 

361 779 

64 281 

475 240 


170 806 

(158 937) 

39 713 

15 125 

28 230 




Total 




789 841 


9 898 463 


253 874 





Adapted from Macey 1982, 



11 



of dairying. The Lower Mainland has a particularly high intensity of animal 
operations, with a large proportion of the hens, chickens, and pigs in the 
province as well as a significant number of cattle. 

REVIEW OF NITROGEN RESEARCH CONDUCTED IN BRITISH COLUMBIA 

Because agriculture in British Columbia is complex and nitrogen processes 
are influenced by weather conditions, the review of research conducted in the 
province was organized into nitrogen management units, which are based on 
natural and imposed moisture conditions. Many different types of moisture 
classifications are available. Clayton and Marshall (Bentley 1979) show that 
British Columbia contains all the soil moisture subclasses that they used for 
Canada. The subclasses include perhumid, humid, subhumid, semiarid, and 
subarid, depending on the varying periods and intensity of water deficit in 
the growing season. This report groups moisture conditions into "aridic" and 
"humidic" nitrogen management units, with no precise definitions proposed at 
this time. The aridic unit includes the interior of the province and the 
humidic the coastal area. The aridic study unit is further broken down into 
subunits, depending on irrigation practices (nonirrigated, irrigated for 
extensive crop production such as forages, and irrigated for intensive crop 
production such as fruit and vegetables). The humidic unit is not further 
subdivided, even though irrigation is used under some conditions. 

Aridic - nonirrigated nitrogen management unit 

The aridic - nonirrigated nitrogen management unit includes farms in the 
Interior and Peace River areas and in some parts of the Okanagan. Animal 
production is significant, making forage an important crop. Forages include 
native grasses, introduced grasses, and cereals. The production of cereals 
and oil seeds is largely confined to the Peace River area, but some of these 
crops are grown in various pockets throughout the management unit. Outside 
the Peace River area, Creston is the most important area for the production of 
cereals and oil seeds. Nitrogen research has been proportional to this 
distribution of agriculture. 

Studies in the late 1950s showed that the quantity and quality of native 
grass (specifically, its protein content) could be increased substantially 
with moderate rates (67 kg/ha) of nitrogen application in the south Okanagan 
(Mason and Miltimore 1959). Beaton et al . (1960) found a poor correlation 
between nitrate accumulation during a laboratory incubation and measured 
forage production in the field. The study did show that nitrate production 
was low on all sites, but nitrogen fertilizer response trials were not 
included. The authors concluded that the wide range of climatic conditions 
probably contributed greatly to the poor correlation. Nitrogen application 
was shown to increase the seed yield of a native range grass (beardless 
wheatgrass) in the south Okanagan (Miltimore et al. 1962). This increased 
seed production was expected to be useful in restoring the dominance of a 
preferred grass species for eventual range improvement. A number of trials 
were subsequently conducted, showing that both yield and nitrogen content of 
grasses of open rangeland were increased by fertilizer application (Hall 1971; 
Mason and Miltimore 1964) and that in some cases there were residual effects 



12 



(Hubbard and Mason 1967; Mason and Miltimore 1969) for up to 10 years (Mason 
and Miltimore 1972). All these factors are important when the economics of 
applications are being considered. Pinegrass was also shown to respond to 
nitrogen applications (Freyman and van Ryswyk 1969). Pinegrass is an 
important summer grazing species that grows in forested areas. These forested 
areas have Gray Wooded soils and freguently respond to sulfur applications as 
well. A sulfur deficiency restricts nitrogen responses. Soil nitrate 
analysis of the pinegrass study showed little movement of nitrogen, even 
through the second season after application. A summary of research on 
rangeland fertilization concluded that nitrogen was the nutrient most 
freguently reguired for range grass production (Agriculture Canada 1971). 
That review concluded, in part, that more fertilizer trials were reguired on 
introduced species of grass and that inexpensive fertilizer application 
methods were reguired for the rough topography of rangelands. 

Several studies have shown that introduced species of range grass such as 
meadow and creeping foxtail, timothy, and crested wheatgrass grown in central 
British Columbia respond readily to nitrogen fertilization (van Adrichem and 
Tingle 1975; Le Pine 1975; Williams et al . 1979; Broersma and Kline 1982; 
Kline and Broersma 1983). Both guantity and guality of the grass were 
improved. Timothy showed some preference to urea over ammonium nitrate, 
whereas reed canarygrass did not (Le Pine 1975). Nitrogen application was 
shown to increase water use efficiency (Williams et al . 1979), which is 
important under dry rangeland conditions. The nitrate content of plants 
was shown to increase with increased rates of nitrogen application, with 
meadow foxtail being the greatest accumulator (Broersma and Kline 1982; Kline 
and Broersma 1983). It was concluded that nitrogen at 120 kg/ha applied in 
the spring and 50 kg/ha applied in the summer would probably not result in 
nitrate accumulation to dangerous levels. A study showed that the crude 
protein content of timothy and meadow foxtail declined from 19 June to 23 
August (advancing maturity) at Prince George (Waldie et al . 1983), but 
corresponding data on the accumulation of dry matter or the availability of 
soil nitrogen were not included. It is evident that as for studies on native 
grasses, nitrogen research on introduced grass species has been directed 
toward plants rather than soils. 

Grass produced in wetlands is an important component of ranching in 
interior British Columbia. These areas are important for grazing and hay 
production, which is critical for over-wintering livestock. Since these areas 
are confined, they can be more intensively managed than rangeland. Fertilizer 
trials on wetlands, both in the field and growth room, showed that nitrogen 
could increase the guantity and guality of forage production (McLean et al . 
1963; Pringle and van Ryswyk 1965, 1967, 1968; Mason and Miltimore 1970; van 
Ryswyk et al . 1973, 1974). This information and other, unpublished data were 
the basis for general fertilizer recommendations for both native and 
introduced grasses (Central Interior Forage Extension Committee 1981). 
Nitrogen applied annually in the fall at a rate of up to 84 kg/ha was 
recommended to reduce nitrogen losses. Most of the research was forage-based, 
and limited information on soil nitrogen has been published. The total amount 
of nitrogen in the soil reported for these studies was high, ranging from 2.3 
to 3.0%, suggesting that most of it was not available to the crop under 
wetland conditions. 



13 



Ashby (1969) found that nitrogen encapsulated in perforated polyethylene 
as a means of controlling the rate of release was more effective than 
soil-applied nitrogen for ryegrass production in the greenhouse. He also 
showed that nitrogen and magnesium were mutually antagonistic in their release 
from the capsules. The technique is not in common use at this time, probably 
because of the high cost of the product. 

Nitrogen research in the Peace River region has been geared toward soils 
rather than toward other areas of management, possibly because of the 
acceptance of the nitrate test for nitrogen fertilizer recommendations in the 
Prairie Provinces. However, crop production and soils in the Peace River 
region are somewhat different from those of the prairies. More grass, 
legumes, flax, and canola are included in the crop rotations, and the soils 
are more acidic. Early published information focused on the effect of 
fertilizer placement on crop production (Nyborg 1961; Nyborg and Hennig 
1969). Seed row applications of fertilizer, including nitrogen, affected 
flax and rapeseed production more than barley, and placement away from the row 
as rates increased was required to reduce seedling damage. Cereal production 
following legume grown for hay was increased in some cases (Hoyt and Hennig 
1971; Hoyt and Leitch 1983). Soil nitrogen measurements appeared to be 
useful in understanding the various responses. Soil nitrate nitrogen appeared 
to be a significant factor in barley production following various dates of 
breaking fescue sod (Hennig and Rice 1977). Acidification of Peace River 
soils has been shown to decrease crop yields. This discovery has implications 
for nitrogen fertilization because most nitrogen fertilizers are net 
acidifiers (Hoyt and Hennig 1982). Liming acid soils was shown to increase 
nitrogen mineralization and nitrification rates (Nyborg and Hoyt 1978). 
Studies on nitrogen fixation showed that it was decreased by low soil pH and 
was influenced by climate, season, and type of plant (Rice et al . 1977; Rice 
1980). 

A limited amount of cereal production is scattered in many locations 
in the aridic - nonimgated study unit of the province. There are few 
published reports of nitrogen trials on cereals in the central and 
southeast part of the province. Gough (1984) did not obtain a yield response 
to nitrogen with spring wheat and spring barley at Armstrong or with spring 
barley at Creston. Soil nitrate, prior to planting, was relatively high 
(90-100 kg/ha to a depth of 50 cm) and may be the reason for a lack of yield 
response. 

Little, if any, research is currently being conducted on nitrogen 
applications on native grasses or on introduced dryland and wetland grasses. 
It is generally assumed that there would be a good response, but operators are 
reluctant to apply fertilizer, except on introduced wetland grasses, because 
there is too much area to cover. In many cases it is more popular to extend 
the land base than to increase the intensity of the management. Fieldwork on 
a soil test correlation project that included nitrogen has been completed in 
the central interior, and the data are currently being assessed (Doggart et 
al . 1983). It is hoped that a soil nitrate test could be used for 
recommendations on fertilizer nitrogen. Some work is being conducted on 
nitrogen fixation by native species of vegetation. 



14 



Only a small amount of research is currently being done on nitrogen in 
cereals outside the Peace River area. The work consists mainly of 
fertilizer response trials in Creston and north Okanagan, where the 
possibility of using a nitrate test is of prime interest. At Beaverlodge 
Research Station, which is on the Alberta side of the Peace River area, 
scientists are studying the relationship between growth and distribution of 
barley root and nitrogen uptake from soils with a solonetizic B horizon, 
i.e., solods; uptake of other nutrients is also being investigated. Work is 
also continuing on nitrogen fixation by legume crops and availability of fixed 
nitrogen to succeeding crops. 

Aridic - irrigated - extensive nitrogen management unit 

Agricultural production in this management unit is sparsely distributed, 
occurring largely in the Okanagan and Interior areas, and is geared to forage 
grass production including grasses, alfalfa, and forage corn. All research on 
the nitrogen requirement of these crops is recent, and publication of data is 
limited. A technical report on field fertilizer response trials showed that 
nitrogen application tends to be the most important nutrient for yield 
increases in silage corn (van Ryswyk 1985). Soil nitrate was measured and 
appeared to be a good indicator for nitrogen recommendations. Although only 
surface (0-15 cm) samples were taken for the response trials, the relationship 
to yield response was quite good. Hilliard (1983) examined one location in 
detail, sampling soil on several dates during the growing season to a depth of 
about 100 cm. The results suggest that nitrate leaching of a treatment that 
contained a high rate of nitrogen (225 kg/ha) occurred during the growing 
season. 

Nitrogen application appears to have influenced magnesium uptake by 
corn, with some evidence of induced magnesium deficiency (Broersma and van 
Ryswyk 1979). The effect appears to differ with the variety of corn and the 
weather. 

Currently, scientists are discussing the implementation of an analysis of 
nitrate in the surface soil to determine how much fertilizer nitrogen is 
required by soils in this management unit. Because crops of relatively low 
value are involved and land area is not a constraint, researchers are seeking 
the most economical method of producing the greatest yield. The inefficient 
use of fertilizer nitrogen resulting from nitrate leaching would be a major 
concern, and therefore plant utilization is emphasized. 

Aridic - irrigated - intensive nitrogen management unit 

Nitrogen research in this management unit has been done mostly in the 
Okanagan area, although production is scattered in other aridic areas. Wilcox 
et al . (1947) documented early observations of fertilizer trials on five apple 
orchards in the Okanagan. The treatments at each location were not 
replicated, hence limiting any statistical treatment. However, the long 
length of the trials (10 years or more) should result in increased confidence 
in the conclusions. The report concluded that nitrogen would increase apple 
production in many Okanagan soils. It was speculated that a leguminous cover 



15 



crop could provide the nitrogen required. Nitrogen applications appeared to 
increase tree vigor (trunk circumference and average terminal length), as well 
as yield and fruit size, but reduced fruit color. Conclusions on the effects 
of nitrogen fertilizer on the soil were limited because sampling was done in 
only 1 year (1940), and the small range of analyses did not include any 
nitrogen measurements. A decreased soil pH resulting from fertilizer 
application was observed. The problems caused by acidification were 
subsequently studied in more detail (Hoyt and Neilsen 1985; Neilsen and Hoyt 
1982; Ross et al . 1985). 

Subsequent work (Wilcox 1949) focused on terminal shoots as a possible 
diagnostic analysis of the nutrient status of apple trees. Evidently, length 
of terminal shoots was being used as a basis for recommendations in nitrogen 
fertilizer. Although significant correlations of the nitrogen content of the 
shoots with terminal length and yield were found, it was concluded that shoot 
analysis was not a suitable means of diagnosing the nutrient status of fruit 
trees. The nitrogen content of the shoot perhaps naturally increased, 
decreased, or fluctuated with time, making sampling time critical, and the 
range of nitrogen values perhaps was not large, despite wide variations in 
soil type and fertilizer treatments of the trees tested. It was suggested by 
the authors that analysis of leaf tissue might be more suitable. 

From the mid 1960s (Mason 1964) to the present (Neilsen and Hogue 1985), 
analysis of leaf tissue has been accepted as a good indicator of the response 
of apple trees to fertilizer applications, including nitrogen. Research on 
nitrogen for apple production in the Okanagan has shifted from yield to yield 
plus quality as the desirable response. Nitrogen was assumed to be an 
important factor affecting yield and quality of apples. There was a trend 
toward using grass as an understory cover crop (Mason 1964), and therefore 
nitrogen studies emphasized the interaction between nitrogen fertilizer and 
understory management on apple yield and quality. Several studies of this 
type showed almost no difference in response to a wide range of nitrogen 
treatments and a moderate range of cultivation treatments (Mason 1969J}). 
Mason speculated further that nitrogen fertilizer may not be necessary in 
orchards of high initial fertility with a grass cover between the rows and may 
be required in only small quantities for today's market requirements of fruit 
color. Concentrations of nitrogen in leaf tissue (Mason 1964) do suggest that 
the orchards were on soils with adequate nitrogen levels, and consequently 
that the grass understory would be beneficial in limiting nitrogen supply to 
apple trees in the fall. Therefore, the quality of the apples, as determined 
by skin color of the fruit and by firmness, would be improved (Mason 1969ja; 
Neilsen et al . 1984). Although lower nitrogen supply in the fall is desirable 
for maintaining apple quality under present marketing criteria (colorful and 
not too big), an adequate supply of nitrogen in the spring appears to be 
required for adequate yield (Mason 1964). Neilsen and Hogue (1985) 
recommended that control of understory vegetation early in the season would be 
necessary to maintain an adequate, well-timed nitrogen supply for optimum 
marketable yields of apples, particularly because previous work (Neilsen et 
al . 1984) showed that apple trees appeared to be more responsive to what was 
done to the soil between the rows than to nitrogen application in the spring. 



16 



Recently, attention has been directed toward the effect of irrigation 
frequency on nutrient uptake of apple trees. Neilsen and Stevenson (1986) 
found that in 1 year out of 4, the concentration of nitrogen in the leaves of 
apple (Summerland Red Mcintosh) trees was higher with daily irrigation than 
with twice-weekly irrigation. They concluded that nitrogen nutrition (as well 
as that of magnesium and zinc) could be improved by high-frequency 
irrigation. This effect would be an additional benefit of trickle irrigation, 
which tends to require frequent water applications. It would be useful to 
know why the increased nitrogen concentration occurred. 

Vegetables and fruit crops other than apples are grown in the Okanagan 
under intensive irrigation practices, but research publications on them 
related to nitrogen are largely absent. Only a study by Molnar (1961) was 
found. His study, which of necessity was short-term, examined the effect of 
nitrogen on peach tree growth but did not include yield measurements. 
Nitrogen applications were shown to extend the length of vegetative growth and 
to increase nitrate nitrogen and the total amount of nitrogen, as well as the 
green and yellow pigment content of leaves, despite the plot area having had a 
history of substantial manure applications plus nitrogen at 45 kg/ha per year 
as fertilizer. 

One general observation about all the reports discussed is that analysis 
of nitrogen directly in the soil was omitted. This limits the interpretation 
of the results. It should be remembered also that all the studies were 
conducted under irrigated conditions, and so the possibility of nitrogen 
application by the irrigation water (water quality) should not be ignored. 
The duration of the studies related to understory management should be 
considered in the interpretation. Since apples are produced for a long period 
of time in a given orchard, a stable nutrient equilibrium may not have been 
fully established in the soil plant system, resulting in differences between 
short- and long-term interpretations. The studies recorded with a grass 
understory did not indicate whether the nitrogen content of grass was 
determined. 

The high intensity of agricultural activity and a growing population have 
put considerable pressure on the quantity and quality of water in the Okanagan 
Basin (Canada - British Columbia Consultative Board 1974). The effects of 
nitrogen, from both agricultural and urban activity, on water quality is an 
area of concern. The efficient use of nitrogen for crop production will be 
required not only for economic crop production (agricultural perspective) but 
also for minimizing the impact of increased nitrogen on general water quality 
(environmental perspective). 

One characteristic of research on orchard crops is that both long- and 
short-term implications must be considered. As a result, a current study is 
measuring the long-term effects of understory management where short-term 
effects were reported earlier (Neilsen et al . 1984; Neilsen and Hogue 1985). 
Cultivars of apples grown also change with time, resulting in a need for 
further research, as with Spartan apple trees, for example. A trial in its 
third year is examining rate of nitrogen (50 and 100 kg/ha), applied at two 
times (spring and fall), and in two forms (urea and NH4NO3) on Spartan apple 



17 



trees. Another trial in its fifth year is examining three nitrogen rates with 
and without phosphorus and potassium and three nitrogen rates with several 
soil-managed treatments. 

Trickle irrigation is being evaluated at this time. Tests are being 
conducted in which nitrogen fertilizer is applied through this system. With 
this approach, timing of nitrogen application is easy, and costs of nitrogen 
applications can be reduced. 

In response to a concern about the water quality of lakes in the Okanagan 
Valley, several studies have been initiated. Lysimeter studies are currently 
in progress at Summerland Research Station to measure nitrogen leaching as a 
result of irrigation. An experiment on Red Delicious and Mcintosh apples and 
on cherries, peaches, and grapes is examining the application of secondary- 
treated effluent by trickle irrigation. This type of irrigation is being 
compared with trickle irrigation using well water with three rates of nitrogen 
applied in the spring. 

Humidic nitrogen management unit 

By 1963, general fertilizer recommendations for this management unit, 
which essentially comprises the Coastal area, appear to have been established 
on the basis of numerous fertilizer response trials and general observations 
(Nelson 1963). At about that time, more site-specific fertilizer 
recommendations were needed, and a soil-test system was gradually developed. 
However, emphasis was directed toward the relatively immobile nutrients (e.g., 
phosphorus, potassium, magnesium, and the micronutrient boron) and as a result 
a soil test for nitrogen has received only limited attention. A general 
recommendation based on past observations and modified according to soil type 
and previous management, particularly manure application, is still largely 
used even though the provincial soil test laboratory routinely includes 
nitrate analysis of soil samples. 

Although numerous fertilizer response trials that include nitrogen have 
been conducted, details of exactly what was done are not available because 
results are published only in brief progress and annual reports (Canada 
Department of Agriculture 1947, 1955, 1957, 1963). Yield response was the 
primary criterion on which the results were interpreted. Negligible plant 
nitrogen uptake and soil nitrogen measurements were made and therefore limited 
understanding of the reasons for these results. 

During this time, research on nitrogen at the University of British 
Columbia was geared toward an understanding of the role of microorganisms on 
nitrogen transformations. Studies on nitrifiers (Sparks 1928), nitrogen 
fixers (West 1937), and actinomycetes (Gilmour 1945) contributed to a general 
understanding of nitrogen processes. 

Many management factors can influence the efficiency of fertilizer 
nitrogen use. In forage production, fertilizer can be applied several times 
during the growing season. Studies have shown that split applications of 
nitrogen on south coastal soils produce little or no differences in total 



18 



yield but tend to result in a redistribution of growth during the growing 
season (Gardner et al . 1960; Maas et al . 1962; Bomke and Bertrand 1983). The 
study of Gardner et al . (1960) showed that Ladino clover in a mixture of grass 
could reduce the fertilizer nitrogen requirement in a nitrogen-deficient 
soil. Bomke and Bertrand (1983) observed a small (8?o) yield advantage of 
ammonium nitrate over urea in only 1 out of 3 years of their study. A spring 
application of nitrogen was shown to affect yield of grass through the growing 
season, with variable interactions with sulfur in the spring compared with the 
fall (Kowalenko 1984d). Soil nitrogen analyses were not recorded in any of 
the reports, making it difficult to determine the reason for the observed 
results. 

Management factors can also influence the efficiency of nitrogen uptake 
by forage corn and hence the forage quality. Fairey (1982) reported that the 
nitrogen content of stover and whole plants was not greatly influenced by 
population density but was closely related to maturity of hybrids at harvest. 
A subsequent report (Fairey 1983) stated that whole-plant nitrogen content 
increased progressively as planting date was delayed. However, the rate of 
increase declined as the harvest date was delayed. In addition, whole-plant 
nitrogen content decreased for each date of planting as the date of harvest 
was delayed. Similar trends were observed for the nitrogen content of stover, 
except that the increases in nitrogen content resulting from delayed planting 
occurred at the same rate for each harvest-date treatment. Nitrogen was not a 
treatment factor for either trial; neither soil nitrogen status nor nitrogen 
fertilization information was provided. The productivity and quality of 
perennial ryegrass was shown to respond to combinations of cutting frequency 
and total rate of nitrogen applied (Fairey 1985). Only limited combinations 
were examined (four cuts with nitrogen at 300 kg/ha and eight cuts at 450 
kg/ha), and residual soil nitrogen was not determined. In a study of the 
accumulation of nitrogen in corn at three locations in 1 year, Loewen (1979) 
found that the most rapid accumulation by the plant occurred 40-70 days after 
planting, which would coincide with the month of 3uly. Accumulated nitrogen 
(excluding roots) ranged from 129 to 167 kg/ha. These studies show the 
complexity of nitrogen in a forage - soil system and the interaction of many 
factors in the final result. 

Nitrogen increases the production of cereal grain, but lodging becomes a 
serious problem under coastal soil and weather conditions. Nitrogen 
application is often restricted, so that crop losses resulting from lodging 
are reduced. The objective then is to fertilize with nitrogen to a level 
where high yields are obtained without increasing the risk of lodging. 
Johnson (1968) was able to produce maximum yield without lodging using Gaines 
wheat with nitrogen at 112-157 kg/ha. It was suggested that Gaines wheat had 
relatively high inherent lodging resistance. This study showed that the 
variety of wheat can influence the effectiveness of nitrogen fertilization of 
wheat. Research reports examining this interaction under conditions in south 
coastal British Columbia are not available. 

Little information has been published on the effect of nitrogen on 
vegetable production in south coastal British Columbia. Freeman (1950) showed 
that nitrogen had a detrimental effect on yield of carrot roots. Nitrogen 



19 



apparently increased the growth of the tops of the plants but did not 
proportionately increase the roots. Nitrogen was also shown to increase the 
carotene content of carrots (Freeman 1951). Maas (1963, 1968) observed that 
nitrogen application could increase yield of potatoes but tended to decrease 
the specific gravity. The rate of release of nitrate nitrogen, as measured in 
growth chamber and laboratory tests in one of these trials, was low in the 
nitrogen-responsive organic soil (Maas 1968). 

Organic soils (peats) are freguently used for highbush blueberry 
production. Herath (1967) showed that waterlogging a peat soil resulted in 
nitrogen deficiency for blueberry plant growth, which produced shorter, more 
compact plants from reduced shoot growth, yellowing, premature leaf aging, and 
low nitrogen levels in the leaves. Analysis of nitrogen in the leaves 
suggested that blueberries preferentially absorbed ammonium over nitrate 
nitrogen. Nitrate at levels exceeding 22 kg/ha resulted in nitrate toxicity 
as shown by severe leaf burn. 

Maas (1967) showed that the total nitrogen content of the surface layer 
of a Vancouver Island peat differed, depending on the substrata. Sedge 
substrata tended to produce sphagnum peat of higher nitrogen content than 
sphagnum substrata. 

Kowalenko (1981a^ found that optimum yield and berry size response by 
raspberries occurred when nitrogen was applied at a rate of 134 kg/ha in a 
field trial in the Abbotsford area. The highest nitrogen treatment rate was 
268 kg/ha. Concentrations of nitrogen in leaf tissue were influenced by 
nitrogen applications, but since there was a gradual decline in the leaves of 
both old and new canes, it was concluded that nitrogen fertilizer 
recommendations based on analysis of leaf tissue would be difficult to 
implement (Kowalenko 1981bK 

Limited data on field plots (Kowalenko and Maas 1982a^, 1982|)) and orchard 
surveys (Kowalenko 1984a, 1984£), which complimented data in the literature, 
have been used as the basis for a method of leaf tissue analysis for 
determining nitrogen (and other fertilizer) reguirements of filberts in 
British Columbia (Kowalenko 1984jd). Nitrogen appears to strongly influence 
the yield of filberts. 

Agricultural production in the lower Fraser Valley is intense. Manure 
production from livestock under this intensive management is high, relative to 
the limited land base available for application. If 1981 census figures for 
number of livestock for the Mainland region are multiplied by an approximate 
amount of nitrogen voided per year, animals would produce nitrogen at a rate 
of 11 292 600 kg/year (Table 5). Assuming no losses and calculating on the 
basis of 81 099 ha of improved farmland for that census region, nitrogen 
production would be equivalent to 139 kg/ha per year. Since nitrogen in 
manure is a valuable resource but also a serious potential environmental 
pollutant, research has increasingly shifted to this aspect in the Lower 
Mainland (Bomke and Lavkulich 1975; Bulley and Holbek 1978; Holbek 1978; 
Maynard and Bomke 1980). A solution to the manure problem was also attempted 
using a simulation model (Bulley and Cappalaere 1978; Cappalaere 1978), where 



20 



Table 5. Number of livestock in south coast mainland of British Columbia 
according to 1981 census* and the calculated manure nitrogen voided per year, 







N voided per 








Number 


animal t 


N voided 


N voided per year 






(g/day) 


(kg/day) 


(kg/300 days) 


Cattle 


159 027 


120 


19 083 


5 724 900 


Hens & chickens 


7 991 733 


1.45 


11 588 


3 476 400 


Turkeys 


595 585 


1.0 


596 


178 800 


Goats 


3 270 


20 


65 


19 500 


Horses 


7 804 


122 


952 


285 600 


Pigs 


158 937 


32 


5 086 


1 525 800 


Sheep 


12 985 


20 


260 


78 000 


Rabbits 


11 681 


1.0 


12 


3 600 


Total 








11 292 600 



♦Adapted from Macey 1982. 
tAdapted from Barber 1979. 

management of manure to minimize nitrogen losses was the major goal. This 
model is being refined to develop guidelines for the management of manure. 
The simulation model is based on rates of various nitrogen processes 
(mineralization, nitrification, denitrification) and water movement in 
soil. Because of the paucity of information on nitrogen processes in local 
soils that can be used for modeling purposes (Harris and Woods 1935; Gardiner 
et al. 1960; Derics 1963; Basaraba 1964a, 1964b; Kowalenko and Lowe 1975, 
1978; Phillips 1976; Hinds and Lowe 1980; Guthrie and Bomke 1980, 1981; 
Guthrie 1981; Lowe and Hinds 1983), data from the literature have been 
extrapolated for estimating rates of nitrogen. Of these studies, only those 
of Harris and Woods (1935) and Guthrie and Bomke (1980) were done in the 
field. 

A recently completed study on the effect of rate and placement of 
anaerobically stored swine slurry on silage corn production showed the 
following: the slurry contributed yield increases that were up to 18?o beyond 
the effects of starter nitrogen, phorphorus, and potassium at soil test 
recommended rates; injection of manure to a depth of 30 cm resulted in 
greater recovery as soil nitrogen in the fall than did surface application; 
and over-the-winter loss of residual nitrate was substantial (Khan 1986). The 
field study was conducted over 3 years and included considerable monitoring of 
nitrogen in the soil. 

The nitrate concentration of groundwater has been extensively measured in 
the lower Fraser Valley, but little has been published. A number of areas in 
the lower Fraser Valley have groundwater with relatively high nitrate 
concentrations (Kohut 1985; Leibscher 1985). Apparently, areas of concern 



21 




Fig. 2. Soil test interpretation zones in British Columbia, 



22 



include Langley - east Surrey, south Abbotsford, Matsqui, and Seabird Island. 
Suspected sources of this nitrate include agricultural activities and sewage 
effluent. Manure stockpiling for poultry, mink, and pig operations are of 
particular concern because of the potentially large and concentrated source of 
nitrate. However, general fertilizer spreading and nitrate contamination of 
surface water are also a concern. 

At the University of British Columbia a project on nitrogen for the 
production of sweet corn is progressing in two parts: the usefulness of 
spring NO3 and NH4 soil analysis is being evaluated for application on corn 
during the early part of the growing season; and the relationship between the 
nitrogen supplying power and various soil properties is being examined. 

The Soils Branch of the British Columbia Ministry of Agriculture and Food 
is continuing the refinement and implementation of manure management 
guidelines. Researchers are using the manure simulation model that was 
recently formulated. 

A private laboratory is conducting exploration of the relative cost of 
various soil analyses that may eventually be considered as an objective basis 
for nitrogen fertilizer recommendations. 

At Agassiz Research Station, several studies on nitrogen are in 
progress. Nitrogen transformations and transport have been monitored under 
fallow conditions where applications were made in the spring and fall. Both 
tracer O^n) and nontracer methods were used. Fieldwork has been completed, 
and laboratory and statistical analyses are in progress. The effect of 
nitrogen on broccoli production is being examined. The study includes a 
comparison of the response and uptake of sweet corn and broccoli to nitrogen. 
A cooperative study between the British Columbia Ministry of Agriculture and 
Food and the University of British Columbia is examining "T-sum" for timing 
the application of nitrogen on grass in the early spring. T-sum is the 
average of the daily maximum and minimum temperatures (degrees C) above zero 
accumulated from 1 January. The system was developed in Great Britain and 
Holland. A soil test monitoring project is also in progress. Results of 
nitrate nitrogen analysis of fall and spring samples will be examined on six 
fields over several years. Replicate analysis of each field will allow the 
determination of field variability and the evaluation of changes over the 
winter. 

OUTLINE OF THE CURRENT SYSTEM OF RECOMMENDATION 

The range and distribution of agriculture has resulted in a complex 
system for the establishment of soil tests and recommendations for British 
Columbia. The provincial soil-testing laboratory has designated a number of 
zones to facilitate interpretations. Several zones are currently used for 
recommendations on nitrogen and other nutrients (Fig. 2). The recommendations 
are further modified by considering the type of crop that is grown. For 
simplicity, 12 crop categories used for nitrogen recommendations are 
illustrated (Table 6), but a much more detailed system has been developed for 
specific crops and for perennial crops of various ages. Plant-oriented 



23 



Table 6. Soil testing laboratory recommendations for maximum nitrogen 
applications on selected categories of crops in interpretation zones of 
British Columbia. 



Crop category 




Zone* 


Rate of N (kg/ha) 


Vegetables 


All 






140 


Ornamentals 


All 






80 


Lawns and gardens 


All 






60 


Fruit trees 


All 






120 


Small fruits 


All 






50 


Grapes 


All 






80 


Cereals 


1, 2 






90 




3, 4, 


5, 


5.01, 6 


70 


Corn (silage) 


1, 2 






40 + 75 




3, 4, 


5, 


5.01, 6 


120 


Grass (established) 


1, 2, 

5 

6 


3, 


4, 5.01 


55(after each cut) 
80 + 55 
90 


Grass - legume 


1, 2, 

5 

6 


3, 


4, 5.01 


55(after each cut) 
80 + 55 
55 


Alfalfa (established) 


1, 2, 

5 

6 


3, 


4, 5.01 


20 
33 
20 


Range (tame grass) 


All 






40 




All 






25 



*1 = Vancouver Island, 2 = Lower Mainland, 3 = Boundary, North and South 
Okanagan, 4 = Southeastern British Columbia, 5.01 = Quesnel, 5 = North Central 
British Columbia, 6 = Peace River. 



Table 7. British Columbia Soil Test Laboratory ratings of surface soil 
nitrate values. 



Soil NO3-N 
Qug/mL) 

Below 11 
11-20 
21-40 
41-50 
51-60 
61-100 
More than 100 



Rating* 

Very low 

Low 

Low medium 

Medium 

High medium 

High 

Very high 



24 



Table 8. Recommmended adjustments by British Columbia Soil Testing Laboratory 
to nitrogen fertilizer rates on tree fruit according to nitrogen 
concentrations (ppm) present in leaves sampled in late June or July. 







N application 


Application 


N applica 


tion 




Age 


increased by 


rate not 


decreased 


by 


Type 


(yrs) 


50% 


20% 


changed 


20% 


50% 


Apples 














Newton & Delicious 


<10 


C1.80 


1.80-2.09 


2.10-2.49 


2.50-2.69 


>2.69 




>11 


<1.80 


1.80-2.09 


2.10-2.19 


2.80-2.99 


>2.99 


Golden Delicious 


Mature 


<1.80 


1.50-1.79 


1.80-1.79 


2.00-2.29 


>2.29 


Mcintosh 


<10 


<1.60 


1.60-1.89 


1.90-2.29 


2.30-2.49 


>2.49 




>11 


<1.60 


1.60-1.89 


1.90-2.59 


2.60-2.79 


>2.79 


Spartan 


CIO 


<1.50 


1.50-1.79 


1.80-2.19 


2.20-2.39 


>2.39 




>11 


<1.5Q 


1.50-1.79 


1.80-2.49 


2.50-2.69 


>2.69 


Winesap 




<1.60 


1.60-1.89 


1.90-2.19 


2.20-2.49 


>2.49 


Others 




<1.60 


1.60-1.89 


1.90-2.29 


2.30-2.59 


>2.59 


Cherries 


<10 


<1.60 


1.60-1.89 


1.90-2.69 


2.70-3.29 


>3.29 




>11 


<1.60 


1.60-1.89 


1.90-2.99 


3.00-3.59 


>3.59 


Pears 


<10 


<1.60 


1.60-1.89 


1.90-2.29 


2.30-2.49 


>2.49 




>11 


<1.60 


1.60-1.89 


1.90-2.49 


2.50-2.69 


>2.69 


Prunes 


<10 


<1.60 


1.60-1.89 


1.90-2.49 


2.50-2.99 


>2.99 




>11 


<1.60 


1.60-1.89 


1.90-2.79 


2.80-3.19 


>3.19 


Peaches 


<10 


<2.00 


2.00-2.59 


2.60-3.19 


3.20-3.79 


>3.19 




>11 


<2.00 


2.00-2.59 


2.60-3.49 


3.50-4.10 


>4.10 


Apricots 


<10 


<2.00 


2.00-2.59 


2.60-3.29 


3.30-3.79 


>3.79 




>11 


<2.00 


2.00-2.59 


2.60-3.49 


3.50-4.10 


>4.10 



25 



Table 9. Recommended adjustments by British Columbia Soil Test Laboratory to nitrogen 
fertilizer rates on grapes according to nitrogen concentrations (ppm) in leaf petioles 
sampled at bloom time. 



Guide 


N application 


Application 


N applic 


ation 


No N 


rate* 


increased 


by 


rate not 
changed 


decreased by 


needed 




5Q?i 


20?6 






20?i 


50?o 




Vinifera labrusca 














and hybrids 














low vigor <0.40 


0.40-0.69 


0.70-0.99 


1.00-1.70 


1.71-1.95 


1.96-2.20 


>2.20 


med vigor <0.40 


0.40-0.69 


0.70-0.90 


0.91-1.60 


1.61-2.00 


2.01-2.49 


>2.49 


high vigor <0.30 


0.30-0.54 


0.55-0.79 


0.80-1.60 


1.61-2.00 


2.01-2.49 


>2.49 


Vinifera vinifera 














low vigor <0.91 


0.91-1.19 


1.20-1.49 


1.50-3.00 


3.01-3.25 


3.26-3.99 


>3.99 


med vigor <1 .40 


1.40-1.64 


1.65-1.90 


1.91-2.70 


2.71-3.00 


3.01-3.69 


>3.69 


high vigor <1 .00 


1.00-1.24 


1.25-1.49 


1.50-3.00 


3.01-3.40 


3.41-3.99 


>3.99 


*See Grape Production Guide 1986, 


British Co 


lumbia Ministry 


of Agriculture and Food, 






Victoria, B.C., for general recommendations on nitrogen application rates. 



Table 10. Comparison of the distribution of fertilizer nitrogen application 
rates with British Columbia Soil Test Laboratory maximum recommended rates 
calculated from 1981 agricultural census for British Columbia. 



Area 



Coastal 

(Lower Mainland) 

Okanagan 

Peace River 

Interior 



Nitrogen ferti 


izer 


Maximum general 


use (kg/ha) 




recommended rate (kg/ha) 


120 




144 


(129) 




(140) 


79 




76 


31 




56 


39 




79 



Total 53 



26 



research and the relatively high rainfall in many areas have resulted in 
nitrogen recommendations that are general rather than specific. Nitrate has 
been included in soil analysis for a number of years, and more recently it has 
been used to modify the general recommendations. The soil nitrate ranges are 
given a rating that is independent of the crop (Table 7). In many cases only 
a general nitrogen recommendation is given, and a precautionary comment is 
made if the soil nitrate value is high. Where soil nitrate values are used, 
recommendations are made by adjusting the maximum nitrogen recommendation 
downward by subtracting twice the soil nitrate value rounded to the nearest 
10. This system has particular application to the Peace River and Interior 
areas, but must be used with extreme caution in other circumstances. Caution 
is required because usually only the surface 15 cm is sampled, the samples are 
not always immediately dried, and sampling time is critical, especially in the 
wetter areas. 

Nitrogen recommendations are also made for fruit trees, grapes, and 
filberts. For fruit trees, leaf analysis is used, and recommendations are 
adjusted according to type and age of the tree (Table 8). In the case of 
apples, each cultivar requires its own recommendations. At present, leaf 
petiole analysis is used for grapes. Recommendations take into consideration 
the species and their vigor (Table 9). Consideration is being given to 
converting from petiole to leaf analysis. The target concentration of 
nitrogen for filbert leaves is not differentiated by age or cultivar of the 
tree. The target concentration was, however, developed for mature trees. In 
all cases, the recommendations for fruit trees, grapes, and filberts are 
mainly upward or downward adjustments to the growers' application rates, but 
general recommendation rates are available in various guides. 

The general approach to recommendations based on soil analysis probably 
reflects the limited soil-based information that is available as well as the 
wet weather, particularly in the winter. More detailed recommendations for 
tree fruits and grapes by analysis of leaf tissue probably reflect the larger 
base of research information and greater confidence in extrapolating data on 
plant analysis (as compared with soil research information) from one location 
to another. 

ASSESSMENT OF FERTILIZER NITROGEN OSE 

An estimate of the distribution of the rate of nitrogen used in the 
province is difficult without an extensive survey of individual farms. Census 
data from 1981 (Macey 1982) do provide information on the rate of fertilizer 
use for each district in the province but do not show the proportion of 
nitrogen used. A calculation using detailed documentation of sales from 1975 
to 1977 (British Columbia Ministry of Agriculture and Food 1979) shows that 
20% of the fertilizer used in the province was nitrogen. By applying this 
proportion to the census data, the rate of nitrogen use was calculated for the 
various areas (Table 10). Also, by using a maximum rate of nitrogen 
recommended by the soil test laboratory and the area of each crop identified 
in the census, a maximum recommended rate for each area was calculated. 



27 



A comparison of these two sets of figures shows that both the Coastal and 
Okanagan areas are using almost the maximum general recommended rate, whereas 
the Peace River and Interior areas use considerably less than the maximum 
(Table 10). This difference probably reflects the intensity of agriculture in 
the various regions. It should be noted that a previous calculation (Table 5) 
showed that sufficient nitrogen was voided from livestock in the Lower 
Mainland to apply it at a rate of 139 kg/ha of improved farmland in the area. 
This finding suggests that even if nitrogen loss of manure averaged 50?o by the 
time it is spread on the land, considerably more nitrogen than the maximum 
recommended is applied. Large amounts of feed such as alfalfa hay and grain 
are imported into the Lower Mainland for intensive management of livestock. 
Livestock are much less concentrated in the Okanagan than in the Lower 
Mainland, and therefore the contribution of nitrogen is lower (nitrogen voided 
at 44 kg/ha of improved farmland). Also, in the Okanagan, sewage resulting 
from urban expansion and the acidifying effect of nitrogen fertilizers on 
orchard soils are causing concern. 

CONCLUSIONS 

Although the calculations used to assess nitrogen fertilizer use in 
British Columbia are approximate, the relative distribution should give an 
accurate picture of the current situation. It is assumed that the pattern of 
use has not changed much since 1981. The figures do show that in general, the 
intensively farmed areas (Coastal and Okanagan) are reaching or exceeding 
maximum recommended rates, whereas less intensively farmed areas (Interior and 
Peace River) are falling below the maximum general recommended rates. A 
review of published research shows that current recommendations are based on 
plant response, and little information on soil analysis data is available. 
The use of soil analysis for nitrogen recommendation can be considered only 
tentative, because of the limited findings available on soil-oriented 
research. Analysis of the leaf tissue of tree fruits, grapes, and filberts is 
well accepted, but little information is available for the interpretation of 
soil analysis. Nitrogen fertilization has been shown to contribute to 
accelerated acidification of Okanagan soils. Efficient nitrogen fertilization 
is needed to limit acidification. 

Nitrogen applications in the Coastal and Okanagan areas are at a level 
that may result in significant problems because of excessive use, such as 
diminishing returns on investments and environmental problems. The high 
concentration of livestock, particularly in the Lower Mainland, will require 
nitrogen from manure to be used as efficiently as possible. Otherwise, manure 
may be viewed as a disposal problem rather than a valuable nutrient source. 
On the other hand, farmers in the Interior and Peace River areas may not be 
fully exploiting the potential economic advantages of increased nitrogen 
fertilizer. Research on soil-based nitrogen, which can be used to provide an 
effective extension program to promote efficient nitrogen use, is limited in 
all regions of the province. Without adequate research, specific 
recommendations for sites with various management histories and various soil 
characteristics will inspire only limited confidence. Research on nitrogen 
needs a different direction and orientation for the varied climate and 
agriculture of British Columbia. At least as much research will be required 



28 



to promote a limit on nitrogen application as will be required to encourage 
increased use. 

Little research has been published on biological nitrogen fixation, 
particularly beyond the Peace River area. Alfalfa is a significant crop in 
the Interior and Okanagan, and the efficiency of the utilization of nitrogen 
fixation has not been assessed. Research on this aspect of nitrogen should be 
encouraged, particularly for extensive farm operations. However, the 
possibility of increasing the use of the nitrogen applied in the Coastal area 
should also be seriously considered. 

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